399840 has 144 divisors (see below), whose sum is σ = 1551312. Its totient is φ = 86016.

The previous prime is 399793. The next prime is 399851. The reversal of 399840 is 48993.

It is a zygodrome in base 2.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 399840.

It is an unprimeable number.

399840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23512 + ... + 23528.

It is an arithmetic number, because the mean of its divisors is an integer number (10773).

2³⁹⁹⁸⁴⁰ is an apocalyptic number.

399840 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 399840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (775656).

399840 is an abundant number, since it is smaller than the sum of its proper divisors (1151472).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

399840 is a wasteful number, since it uses less digits than its factorization.

399840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49 (or 34 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 33.

The square root of 399840 is about 632.3290282756. The cubic root of 399840 is about 73.6708045786.

The spelling of 399840 in words is "three hundred ninety-nine thousand, eight hundred forty".